FeS2/CoS2 Interface Nanosheets as Efficient Bifunctional Electrocatalyst for Overall Water Splitting

Electrochemical water splitting to produce hydrogen and oxygen, as an important reaction for renewable energy storage, needs highly efficient and stable catalysts. Herein, FeS2/CoS2 interface nanosheets (NSs) as efficient bifunctional electrocatalysts for overall water splitting are reported. The thickness and interface disordered structure with rich defects of FeS2/CoS2 NSs are confirmed by atomic force microscopy and high‐resolution transmission electron microscopy. Furthermore, extended X‐ray absorption fine structure spectroscopy clarifies that FeS2/CoS2 NSs with sulfur vacancies, which can further increase electrocatalytic performance. Benefiting from the interface nanosheets' structure with abundant defects, the FeS2/CoS2 NSs show remarkable hydrogen evolution reaction (HER) performance with a low overpotential of 78.2 mV at 10 mA cm−2 and a superior stability for 80 h in 1.0 m KOH, and an overpotential of 302 mV at 100 mA cm−2 for the oxygen evolution reaction (OER). More importantly, the FeS2/CoS2 NSs display excellent performance for overall water splitting with a voltage of 1.47 V to achieve current density of 10 mA cm−2 and maintain the activity for at least 21 h. The present work highlights the importance of engineering interface nanosheets with rich defects based on transition metal dichalcogenides for boosting the HER and OER performance. FeS2/CoS2 interface nanosheets with rich defects show excellent electrocatalytic performance for hydrogen evolution reaction and oxygen evolution reaction in alkaline electrolytes. The overall water splitting device built with FeS2/CoS2 nanosheets as both cathode and anode also shows an excellent performance.